Testing rules with emulator in Firebase - Mini Project: Build & Apply

Testing rules with emulator

📖 Scenario: You are setting up Firebase security rules for a simple app. You want to test these rules locally using the Firebase Emulator to make sure your data is safe before deploying.

🎯 Goal: Build a Firebase security rules file and test it using the Firebase Emulator. You will create a basic rule, configure the emulator, write a test case, and complete the setup to run the emulator.

📋 What You'll Learn

Create a Firebase security rules file named firestore.rules with a simple read rule

Add an emulator configuration in firebase.json to enable Firestore emulator

Write a test script in test.rules.js to check the read rule using the emulator

Complete the firebase.json file with the emulator port and rules path

💡 Why This Matters

🌍 Real World

Testing Firebase security rules locally helps prevent data leaks and unauthorized access before deploying to production.

💼 Career

Firebase developers and cloud engineers use emulators to safely test security rules and app behavior during development.

1

Create basic Firestore security rules

Create a file named firestore.rules with these exact contents: rules_version = '2'; and service cloud.firestore { match /databases/{database}/documents { match /test/{doc} { allow read: if true; } } }

Firebase

# Your code here

Need a hint?

Start with the rules version, then define the service and match paths exactly as shown.

2

Configure Firestore emulator in firebase.json

Add a firestore section inside emulators in firebase.json with port set to 8080 and rules set to firestore.rules

Firebase

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    match /test/{doc} {
      allow read: if true;
    }
  }
}

{
  "emulators": {
    // Your code here
  }
}

Need a hint?

Inside the emulators object, add the firestore key with the port and rules file path.

3

Write a test script to check read access

Create a file named test.rules.js and write code that imports @firebase/rules-unit-testing, initializes a test app with project ID demo-project and Firestore emulator at port 8080, then attempts to read from test/doc1 collection using assertSucceeds

Firebase

// Your code here

Need a hint?

Use initializeTestEnvironment with the project ID and emulator port, then test reading the document with assertSucceeds.

4

Complete firebase.json with emulator settings

Add the emulators section to firebase.json with firestore emulator on port 8080 and rules set to firestore.rules, and add ui emulator on port 4000

Firebase

{
  "emulators": {
    "firestore": {
      "port": 8080,
      "rules": "firestore.rules"
    },
    // Your code here
  }
}

Need a hint?

Add the UI emulator settings inside the emulators object with enabled true and port 4000.